Biomedical neutron research at the Californium User Facility for Neutron Science

The Californium User Facility for Neutron Science has been established at Oak Ridge National Laboratory (ORNL). The Californium Use Facility (CUF) is a part of the larger Californium Facility, which fabricates and stores compact²⁵²Cf neutron sources for worldwide distribution. The CUF can provide a cost-effective option for research with²⁵²Cf sources. Three projects at the CUF that demonstrate the versatility of²⁵²Cf for biological and biomedical neutron-based research are described: future establishment of a²⁵²Cf-based neutron activation analysis system, ongoing work to produce miniature high-intensity, remotely afterloaded²⁵²Cf sources for tumors therapy, and a recent experiment that irradiated living human lung cancer cells impregnated with experimental boron compounds to test their effectiveness for boron neutron capture therapy.     

Neutron-activation analysis of vanadium in oils with californium-252

Results are given which have been obtained by the application of relatively small²⁵²Cf sources for the neutron-activation analysis of vanadium in oils. It could be shown that by optimization the geometrical conditions for activation and counting with a 24 μg²⁵²Cf source detection limits down to the order of 1 ppm vanadium are attainable; the absolute error, e.g., at 1.3 ppm is 0.32 ppm.     

Comparison between the minimum detection limits of radioisotope X-ray fluorescence technique and activation analysiś with a low intensity252Cf neutron source

A comparative study of radioactive X-ray fluorescence and neutron activation analysis using a low-intensity²⁵²Cf source has been carried out. X-ray fluorescence proved to be superior to NAA if ion-exchange preconcentration preceds the instrumental method, while less difference in the minimum detectable limit was found in direct analysis of aqueous solutions.     

Neutron activation analysis applications at the Savannah River Site using an isotopic neutron source

NAA using ²⁵²Cf is used to address important areas of applied interest of the Savanah River Site (SRS). Sensitivity needs for many of the applications are not severe; analyses are accomplished using a 21 mg ²⁵²Cf NAA facility. Because NAA allows analysis of bulk samples, it offers strong advantages for samples in difficult-to-digest matrices when its sensitivity is sufficient. Following radiochemical separation with stable carrier addition, chemical yields for a number of methods are determined by neutron activation of the stable carrier. In some of the cases where no suitable stable carriers exist, the source has been used to generate radioactive tracers to yield separations.     

Activation analysis of halogens in photographic emulsions using a252Cf neutron multiplier

A nondestructive neutron activation technique for the simultaneous direct determination of chlorine, bromine, and iodine in silver halide mixtures is described using a²⁵²Cf neutron multiplier (CFX). About 5–50 mg of sample are used. The analysis is semiroutine, without the need for a monitor included with each sample since the flux stability and reproducibility are within ±1%, decaying only with the 2.65 year half-life of²⁵²Cf. The precision and accuracy are counting-statistics controlled and are generally ±1% RSD or better. The method offers an attractive alternative to existing chemical and instrumental methods for these determinations in silver halide mixtures because it has the potential for providing reasonably rapid analyses with good precision and accuracy.     

Thermal neutron activation analysis of different varieties of mustard and sunflower seeds

Neutron activation analysis (NAA) technique has been used for the estimation of Mn, Na, and K in different varieties of oil seeds of mustard and sunflower in India. The samples were irradiated in a²⁵²Cf source with neutron flux of 10⁹ n s^–1 and the analysis was done using a multichannel analyzer (MCA) coupled to high purity germanium (HPGe) detector. Different varieties of seeds are found to have different concentrations of tracer elements when compared among themselves.     

Quantitative 252Cf plasma desorption mass spectrometry for pharmaceuticals: A new approach to coupling liquid chromatography with mass spectrometry

A ²⁵²Cf plasma desorption mass spectrometer has been set up to analyse thin layers of non-volatile organic samples. Molecular and fragment ions were produced and their mass was determined by a time-of-flight measurement. A novel interface combines a high-performance liquid chromatograph with the ²⁵²Cf plasma desorption mass spectrometer in a twofold way: introducing the effluent continuously through a capillary inlet in the on-line liquid chromatography mass spectrometry mode or transferring already prepared samples through a vacuum lock into the mass spectrometer in the off-line liquid chromatography+mass spectrometry mode. The off-line mode has been applied for the quantitative analysis of pharmaceuticals in blood using stable isotope labelled standards.     

Einsatz Verschiedener Neutronenquellen zur Analytischen Nutzung Prompter Neutroneneinfanggammastrahlung

The analytical use of the prompt gamma-rays originating from neutron capture is a valuable completition of the conventional neutron activation analysis. The application of the external radiation tube P2 of the research reactor in Munich, an Am—Be neutron source of 300 mCi and a 1 mg²⁵²Cf neutron source is discussed.      

Sol particle immunoassays using colloidal gold and neutron activation

The feasibility of performing immunoassays with colloidal gold labels and detection of¹⁹⁸Au by neutron activation has been demonstrated with measurements of human immunoglobulin and of serum antibodies to human immunodeficiency virus type 1. The detection sensitivity achieved after activation in a high flux reactor or with a water moderated²⁵²Cf source, by gamma-counting or by autoradiography, is similar to the sensitivity obtained with absorbance measurements in the more common enzyme immunoassays. The reactor based neutron activation assay allows detection of 10^–16 mol of analyte in routine operation with possible extension to 10^–20 mol. The sensitivity with the 1.3 Ci²⁵²Cf source is limited to about 10^–15 mol. The practical limitations of the assay's sensitivity at this point are due to background signals from reagents and/or nonspecific binding of the gold labeled reagent.     

The application of a252Cf neutron multiplier for routine instrumental neutron activation analysis

The successful application of instrumental neutron activation analysis for routine determinations depends on the ability to produce accurate and precise analytical results in a relatively short time. An important factor in obtaining the desired speed has been the availability of a low-cost, moderate-flux neutron source for on-site use. The²⁵²Cf neutron multiplier (CFX), designed and constructed by Intelcom Rad Tech Corporation of San Diego, California, is a subcritical assembly capable of continuous, stable operation and has provided us with the ability to determine more than 35 elements as major and minor components. The CFX produces a thermal neutron flux of ∼2×10³ n/cm²-sec by a 100-fold multiplication of the neutrons emitted from a 1 mg²⁵²Cf source. Of particular importance in its application at Kodak has been the determination of the halogens Cl, Br, and I, both singly and simultaneously, in various matrices including photographic materials.     

Fabrication of 50-mg252Cf neutron sources for the FDA activation analysis facility

The Transuranium Processing Plant (TPP) at the Oak Ridge National Laboratory (ORNL) has been requested by the Food and Drug Administration (FDA) to furnish 200 mg of²⁵²Cf for use in their new activation analysis facility. This paper discusses the procedure to be employed in fabricating the californium into four neutron sources, each containing a nominal 50-mg of²⁵²Cf. The completed neutron sources will be assayed using a precision fast-neutron counter, decontaminated and loaded into a concreete-shielded shipping container weighing 10.7 Mg for shipment to the FDA facility located at Howard University in Washington, D. C.Research sponsored by the Office of Basic Energy Sciences, U. S. Department of Energy, under contract DE-AC05-840R21400 with Martin Marietta Energy Systems, Inc.     

Determination of some macro and micro nutrients in soils of Maharashtra State by instrumental neutron activation analysis using 252Cf as a thermal neutron source

Some macro and micronutrients in soils from some districts of Maharashtra State have been determined by instrumental neutron activation analysis. Neutrons from ²⁵²Cf have been used for irradiation. The activity induced was measured by a HPGe detector coupled to a MCA unit. The statistical evaluation of the method has been explained. This revised version was published online in August 2006 with corrections to the Cover Date.     

Eine 3mg-252Cf-Bestrahlungsanordnung-Aufbau und Anwendungen

In the last years Cf-252 neutron sources will be incresingly used for nuclear analytical purposes. In the Central Institute of Isotope and Radiation Research, Leipzig, an irradiation equipment with a 3mg²⁵²Cf neutron source was constructed. It reaches thermal neutron fluxes of about 10⁷ n·cm^–2·s^–1. The construction of this equipment and the different moderation geometries are described. Possibilities of the application for neutron induced autoradiography, neutron radiography and neutron activation analysis are demonstrated on examples.     

A method for bulk hydrogen analysis based on transmission and back scattering of fast neutrons

A method was proposed for bulk hydrogen analysis. It is based on simultaneous detection of transmitted fast neutrons and back scattered thermal neutrons from the investigated samples by ³He detectors. The fast neutron beams were obtained from ²⁵²Cf and Pu–Be neutron sources. The experimental set-up as well as samples preparation were described. Incident thermal neutrons beams obtained from either ²⁵²Cf or Pu–Be sources, were used to investigate the samples by neutron backscattering. The results obtained from transmission and backscattering of fast neutrons were compared and discussed. The advantage and capabilities of the proposed method were presented. The results obtained using fast neutron beams are more sensitive than those obtained using thermal neutron beams. Validation procedures were proposed to credit the results.     

Instrumental neutron activation analysis of some ancient punchmark coins from India

A nondestructive instrumental neutron activation analysis technique is applied for the analysis of precious ancient punchmark coins. Coins ranging between 8th century B.C. to 2nd century B.C. were irradiated with thermal neutrons in a²⁵²Cf neutron source facility and analyzed by comparator method of instrumental neutron activation analysis, using high purity germanium detector coupled to a multichannel analyzer, the activities being measured at photopeak energies of the corresponding radioisotopes. It is observed that punchmark coins are mainly of two types: copper or silver based. Other elements present in varying proportions are gold, arsenic and antimony.     

Instrumental neutron activation determination of rare earth,noble and other elements in mineral raw materials of The Socialist Republic of Vietnam

The possibilities of multielement neutron activation analysis of the mineral raw materials of the Socialist Republic of Vietnam, have been studied. Samples were activated by a²⁵²Cf neutron source (yield 4·10⁹ n·s^–1). The induced activity was measured by coaxial Ge(Li) and planar Ge detectors. The content of gold, thorium, uranium, rare earths and other elements, was determined and evaluated in ores and concentrates by an absolute method.     

Experimental Evaluation of a Portable Neutron-Based Gamma-Spectroscopy System for Chloride Measurements in Reinforced Concrete

A portable prompt gamma neutron activation (PGNA) spectroscopy system has been developed to analyze the elemental composition (Ca, Si, Al, etc.) of reinforced concrete and to measure chloride contamination. The portable PGNA system consists of a high purity germanium (HPGe) gamma detector with a 70% relative efficiency, a ²⁵²Cf neutron source and moderator subsystem, and a portable multichannel analyzer system integrated with a laptop computer. Two types of activation experiments were performed to evaluate the device: first, a detector calibration using a Cl gamma standard provided by a PGNA facility; second, an evaluation of the actual performance of the complete system with the ²⁵²Cf source using full scale test slabs containing known amounts of chloride. Both methods indicate that it is feasible to use this device to measure the chloride content of reinforced concrete in the field. The chloride level for the corrosion threshold can be measured with a precision of 10% for a counting time of roughly 6 minutes. This makes the PGNA method competitive with the conventional destructive method.     

Determination of Fluorine in Vegetation by Proton Activation Analysis

Abstract

Techniques have been developed for proton activation analysis using the ¹⁹F(p,p′y)¹⁹F reaction to measure the fluorine content of pulverized samples of vegetation which have been exposed to fluorides in the atmosphere or soil. The method is non-destructive and neither the chemical form of fluorine in the sample nor the type of vegetation analyzed appears to affect results. Calibration is performed by analyzing samples to which known amounts of fluorine are added. The fluorine content of 11 vegetation samples was determined by proton activation analysis and by standard chemical techniques. The values obtained by the two methods were in generally good agreement. Fluorine concentrations greater than 1 ppm can be measured with uncertainties ranging from about 50% at 5 ppm to less than 10% at concentrations above 50 ppm.     

Determination of Mn and Na in geological samples

Neutron activation technique using a low intensity²⁵²Cf source has been applied for Mn and Na analysis in geological samples. The series of samples tested in the present work were collected from the boreholes Nádudvar-9, Hajdúböszörmény-1 and Nagyecsed-1 in Hungary, from different strata.     

Determination of major and trace elements in crude oils by neutron activation and reflection methods

The concentrations of O, Na, Cl, V, Mn and Ni in crude oils of different origins were determined, using sampling (SNAA) and on-stream (ONAA) activation analyses. Samples were irradiated with thermal and fast neutrons produced by a 0.3 mg²⁵²Cf source and a 14 MeV generator. The H-content and the C/H atomic ratio have been determined by thermal neutron reflection method using an 18 GBq Pu−Be source. This work was supported in part by the Hungarian Academy of Sciences.